Instrumentation for the surgical correction of human thoracic and lumbar spinal disease from the lateral aspect of the spine

ABSTRACT

An improved method and instrumentation for performing spinal surgery, including discectomy, interbody fusion and rigid internal fixation of the spine, from the lateral aspect of the spine is disclosed. The surgical procedure can be performed through a very small incision. The instrumentation of the present invention, all of which is inserted from a lateral position into the spine in the preferred embodiment, comprises a guide pin, a distractor, an extended outer sleeve, an inner sleeve an adjustable drill and an implant driver. The distractor of the present invention is driven into the disc for spacing apart and realigning the adjacent vertebrae. It further functions as an alignment rod for inserting the extended outer sleeve which is a hollow tubular member capable of maintaining said spacing and alignment of two adjacent vertebrae and defines a protected space through which subsequent instruments which may include, but are not limited to, a drill and a diameter reducing inner sleeve may be passed, as well as a spinal implant. The remainder of the surgical procedure consisting of the removal of spinal material across the disc, fusion, and rigid internal stabilization via the implant may all be performed via the closed space within the extended outer sleeve.

RELATED APPLICATIONS

This application is a division of application Ser. No. 08/394,836, filedon Feb. 27, 1995, now U.S. Pat. No. 5,772,661 which is acontinuation-in-part of Ser. No. 08/074,781, filed on Jun. 10, 1993, nowU.S. Pat. No. 5,484,437 which is a continuation in part of Ser. No.07/968,240, filed on Oct. 29, 1992, now U.S. Pat. No. 5,741,253 which isa continuation of Ser. No. 07/698,674, filed May 10, 1991, which is adivisional of Ser. No. 07/205,935 now abandoned, filed on Jun. 13, 1988,now issued U.S. Pat. No. 5,015,247; and a continuation in part of Ser.No. 08/219,626, filed Mar. 28, 1994 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to instrumentation and methodsof performing surgical procedures on the human thoracic and lumbar spinealong the lateral aspect of the spine and from a true lateral oranterolateral approach, and specifically to the surgical correction ofthoracic and lumbar disc disease and spinal deformities whereconcomitant fusion is desired.

2. Description of the Related Art

As regards the thoracic spine, it may be afflicted with a variety ofailments, some so severe as to require surgical intervention. A discherniation may compress the spinal cord and/or nerve roots and causepain, loss of function, and even complete paralysis of the legs withloss of bowel and bladder control. The correct treatment for suchconditions is the removal of the offending discal tissue. However, thishas proven both difficult and quite dangerous. When the discs of thethoracic spine are approached posteriorly (from behind) the spinal cordis in the way. To approach the same herniation anteriorly (from thefront) requires the very formidable procedure of thoracotomy (cuttingopen the chest) and moving the heart and lungs out of the way.

Quite recently surgeons have begun performing these procedures from alateral approach to the spine (from the side) using fiber optic viewinginstruments called thorascopes and numerous small surgical openingsthrough the chest wall (portals) through which various surgicalinstruments, such as burrs, rongeurs and curettes, may be placed toremove these disc herniations while avoiding formal thoracotomy. Becausethe discs are very narrow in the thoracic spine and the surgeon isapproaching the spine laterally, there is very little space in which towork as the disc is entered in order to get to the back of the discspace. Therefore, the amount of disc removal may be limited. In thealternative, the surgeon might remove the pedicle to gain access to thespinal canal risking further weakening of the already diseased area.

Sometimes, for a variety of reasons including the removal of discmaterial, the thoracic spine may become unstable (too much motion) atany given level. Historically, this has been treated by fusion, thejoining together permanently of the unstable vertebrae via a bridge ofbone so as to eliminate all motion at that location. Fusions about thethoracic spine have been performed either anteriorly or posteriorly,either procedure being a rather large surgical undertaking.

Stability of the spine is required for fusion to occur. For this reason,and for the purpose of correcting spinal deformity, it is oftennecessary to use hardware to rigidly internally fixate (stabilize) thespine. To date, the only benefit the use of the thorascope has providedin this regard is to allow the previous thoracotomy incision to besomewhat smaller.

So to date the following problems remain even utilizing the most recenttechnology as regards the surgical treatment of thoracic disc disease:

Firstly, the working space within the disc itself to access theherniation which is more posterior is quite limited.

Secondly, multiple or long incisions through the chest are stillrequired.

Thirdly, when fusion is required a major surgical undertaking with itsconsiderable risks is required.

Fourthly, the installation of hardware affixed to the spine stillrequires a thoracotomy, albeit a smaller one if visualization isassisted via the thorascope.

Fifthly, when, as is often the case, the patient requires all three,that is, discectomy (excision, in part or whole, of an intervertebraldisc), fusion, and the application of hardware to the spine, thoseprocedures are performed as serially (one after the other) combinedsurgical procedures with added surgical times, complications,morbidities, and mortalities.

As regards to the human lumbar spine, the treatment of discal diseasewith neural compression has generally been from a posterior (frombehind) approach. This is sensible as the lumbar discs are generallyquite large and it is only those protrusions occurring posteriorly whichcompress the neural elements which are themselves posterior to thediscs. These posterior approaches have included both true posteriorapproaches and posterolateral approaches to the discs. Further, suchapproaches have been made via open incisions or through percutaneousstab wounds. In the latter case, instruments are inserted through thestab wounds and monitored by the use of radiographic imaging or the useof an endoscopic viewing device. While it is possible to also decompressa posterior disc herniation in the lumbar spine from an anteriorapproach (from the front) doing so requires the removal of a verysubstantial portion or all of the disc material in the front and midportions of the disc thus leaving that disc incompetent and that spinalsegment generally unstable. Therefore, such an anterior approach to thelumbar spine has been reserved for those instances where a fusion is tobe performed in conjunction with, and following such a disc removal.

As regards to fusion, the application of bone or bone like substancesbetween bones to induce bony bridging, such procedures have beenperformed outside the vertebral bodies and/or between the vertebralbodies. The latter being known as an interbody fusion. Such interbodyfusions have been performed from posterior, posterolateral and anterior.The adjective applying specifically to the direction from which the bonegrafts enter the intervertebral space. Interbody fusion from theposterior approach while still in use has been associated withsignificant complications generally related to the fact that thedelicate dural sac and the spine nerves cover the back of the disc spaceand are thus clearly in harms way with such an approach. Theposterolateral approach has generally been utilized as a compliment topercutaneous discectomy and has consisted of pushing tiny fragments ofmorsalized bone down through a tube and into the disc space.

Anterior interbody spinal fusion is performed from a straight anteriorposition as regards the path of entry of the fusion material into theintervertebral space. Such an anterior position is achieved in one oftwo ways. First, by a straight anterior approach which requires that theperitoneal cavity, which contains the intestines and other organs, bepunctured twice, once through the front and once through the back on theway to the front of the spine; or secondly, by starting on the front ofthe abdomen off to one side and dissecting behind the peritoneal cavityon the way to the front of the spine. Regardless of which approach tothe front of the spine is used, and apart from the obvious dangersrelated to the dense anatomy and vital structures in that area, thereare at least two major problems specific to the anterior interbodyfusion angle of implant insertion itself. First, generally at the L₄L₅disc, the great iliac vessels bifurcate from the inferior vena cava liein close apposition to, and, covering that disc space making fusion fromthe front both difficult and dangerous. Secondly, anterior fusions havegenerally been done by filling the disc space with bone or by drillingacross the disc space and then filling those holes with cylindricalimplants. As presently practiced, the preferred method of filling thedisc space consists of placing a ring of allograft (bone not from thepatient) femur into that disc space. An attempt to get good fill of thedisc space places the sympathetic nerves along the sides of the disc atgreat risk. Alternatively, when the dowel technique is used, because ofthe short path from the front of the vertebrae to the back and becauseof the height of the disc as compared to the width of the spine, only aportion of the cylindrical implant or implants actually engages thevertebrae, thus, compromising the support provided to the vertebrae andthe area of contact provided for the fusion to occur.

There is therefore, in regard to the lumbar spine, a need for a newmethod and means for achieving interbody fusion which method avoids theproblems associated with all prior methods, and which have included, butare not limited to, nerve damage when performed posteriorly, or the needto mobilize the great vessels when performed anteriorly. Further, thesize of the implants are limited by the dural sac posteriorly, and thewidth of the spine and the delicate vital structures therewithassociated anteriorly. An improved method and means for interbody fusionshould provide for optimal fill of the interspace without endangeringthe associated structures and allow for the optimal area of contactbetween the implant or implants and the vertebrae to be fused.

SUMMARY OF THE INVENTION

The present invention is directed to methods and instrumentation forperforming surgery on the spine along its lateral aspect (side) andgenerally by a lateral or an anterolateral surgical approach, such thatthe instruments enter the body from an approach that is other thanposterior and make contact with the spine along its lateral aspect. Thepresent invention provides for the entire surgical procedure to beperformed through a relatively small incision and may be performed ineither the thoracic or lumbar spine.

In the preferred embodiment, the instrumentation of the presentinvention comprises a guide pin, a distractor, an extended outer sleeve,an inner sleeve and drill adjustable for depth and with a depth limitingmeans. The distractor of the present invention is used for initiallydistracting (spacing apart) and realigning adjacent vertebrae of thespine and also functions as an alignment rod for inserting the extendedouter sleeve. The distractor is placed at the affected disc spacebetween adjacent vertebrae through a small incision in the body. Forexample, for surgery in the thoracic spine, a small incision in thechest cavity of the patient is made from a lateral approach to thethoracic spine. For surgery in the lumbar spine a small incision may bemade in the abdominal wall of the patient. The insertion of thedistractor may be guided by a guide pin previously inserted in the discspace and visually monitored for proper orientation and placement by thesurgeon either indirectly through an image intensifier, or directlythrough a thorascope or by direct vision.

The extended outer sleeve in the preferred embodiment is a hollowtubular member having an extension member that is inserted in the discspace and is capable of distracting and aligning the two adjacentvertebrae from the lateral aspect of the spine. In the preferredembodiment, the extended outer sleeve has a pair of prongs for fixedlyengaging the two adjacent vertebrae and further stabilizing the adjacentvertebrae. With the distractor in place in the affected disc space, theextended outer sleeve is placed over the distractor, and the distractorguides and aligns the insertion of the extended outer sleeve. As theextended outer sleeve is seated, the extension member becomes insertedin the disc space and the prongs engage the outside wall of the adjacentvertebrae. The distractor is then removed and the extended outer sleevemaintains the proper distraction and alignment of the adjacentvertebrae. The remainder of the surgical procedure consisting of discremoval, fusion, and rigid internal stabilization may all be performedvia the closed space within the extended outer sleeve. Alternatively, aconvertible extended outer sleeve comprising a hollow tubular memberthat can be dissociated from its insertion end which remains engaged tothe vertebrae to maintain distraction and alignment, may be used whereit is desired to have direct visualization and access to the surgicalsite for at least a portion of the surgical procedure.

The drilling out and the subsequent removal of a rather significant massof the disc itself may be curative in relieving a posterior discherniation as the mass of tissue pushing from within the disc outwardand posteriorly is thus removed. Further, the distractor in driving thevertebrae apart exerts significant tension on the walls of the discwhich are pulled straight also tending to correct any disc herniation.Finally, since the hole drilled across the disc space is quite close tothe posterior borders of the vertebrae, it makes the removal of anypersisting posterior disc herniation quite simple. With the drillremoved and the extended outer sleeve cleaned out by irrigation andsuction, one can then place the endoscope directly down the outer sleeveand into the large space created by the removal of the disc, and in thepreferred method, the adjacent vertebral bone, and then remove anyremaining fragments of disc using conventional hand held instrumentssuch as rongeurs and curettes under endoscopic visualization.

When it is desirable to remove posterior disc material, then aspecialized modification of the extended outer sleeve having at itsdistal end a spine engaging portion comprising one anterior extensionand posteriorly two prongs one each above and below the disc space maybe used. Further, such an extended outer sleeve may be configured suchthat the great length of the hollow tubular portion of the extendedouter sleeve is detachable, as by unscrewing, from the distal workingend such that when uncoupled the distal end may remain in placemaintaining distraction even after the hole is drilled and thus allowingthe surgeon to work through that remaining portion of the extended outersleeve and the space provided by the drilling to remove the posteriordisc material under direct vision. For those instances where the surgeonhas elected to access the spine through a more standard incision and isviewing the spine directly, the surgeon is then able to continue tooperate through the distal spine engaging portion of the extended outersleeve and still maintain the distraction and alignment of thevertebrae.

A spinal implant may then be inserted through the extended outer sleeveand into the hole in the adjacent vertebrae. The extended outer sleeveis removed once the spinal implant has been inserted. If the spinalimplant being inserted has surface projections such as a thread, then aninner sleeve is inserted in the extended outer sleeve prior to drillingto accommodate the height of the projections or as in the case of athread, the difference between the major and minor diameters of theimplant.

To further stabilize the spinal implant, a staple alignment rod may bemechanically coupled to the spinal implant prior to the removal of theextended outer sleeve. The extended outer sleeve is then removed and astaple having spine engaging prongs is inserted via the alignment rodand is coupled to the spinal implant. The alignment rod is removed andreplaced with a locking screw to secure the staple to the spinalimplant.

While the preferred method utilizing a cylindrical implant and involvingthe removal of some bone from each of the adjacent vertebrae inpreparation for fusion has been described, it is understood that thedistractor and sleeve could as well be rectangular and the drillsupplemented with or replaced by a box chisel, or other chisel so as toproduce a rectangular fusion site or similarly any of a variety ofshapes. Further, it is understood that the outer sleeve could bedimensioned so as to confine the removal of the disc material,regardless of the means, to the area between the adjacent vertebraerather than providing for the removal of the bone as well.

OBJECTS OF THE PRESENT INVENTION

It is an object of the present invention to provide instrumentation forperforming surgery on the thoracic spine through the chest cavity from alateral approach to the spine.

It is another object of the present invention to provide a method ofperforming surgery on the thoracic spine through the chest cavity from alateral approach to the spine that is safer, more effective and fasterthan previously possible.

It is a further object of the present invention to provideinstrumentation and method of inserting a spinal implant in a holedrilled across the disc space and into two adjacent vertebrae of thethoracic spine through the chest cavity from a lateral approach to thespine.

It is another object of the present invention to provide for a methodand instrumentation for performing a thoracic discectomy, an interbodyfusion, and rigid internal fixation of the spine through the chestcavity from a lateral approach and all as a single integrated procedure.

It is yet another object of the present invention to provide for amethod and instrumentation for performing a lumbar fusion from thelateral aspect of the spine.

It is further another object of the present invention to provide for amethod and instrumentation for performing a lumbar fusion and spinalcanal decompression from the lateral aspect of the spine.

It is further still another object of the present invention to providefor a method and instrumentation for performing a lumbar fusion,decompressive discectomy, and a rigid internal fixation of the spine andall as a single integrated surgical procedure.

It is further yet another object of the present invention to provide fora method and instrumentation to achieve discectomy, fusion and interbodystabilization of the lumbar without the need to mobilize the greatvessels from the front of the vertebral bodies.

These and other objects of the present invention will become apparentfrom a review of the accompanying drawings and the detailed descriptionof the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a rear perspective view of a segment of the thoracic spinewith the guide pin of the present invention about to be inserted from alateral approach to the thoracic spine into the disc space between twoadjacent vertebrae.

FIG. 2 is a rear perspective view of a segment of the thoracic spinewith the guide pin inserted in the disc space between two adjacentvertebrae and the distractor of the present invention about to be placedover the guide pin.

FIG. 3 is an enlarged front elevational view of a segment of thethoracic spine along line 3 of FIG. 2 having a portion of the topvertebrae removed and a portion of the disc removed with the guide pin,shown partially in hidden line, inserted from a lateral approach to thethoracic spine into the disc space.

FIG. 4 is an enlarged front elevational view of the segment of thethoracic spine of FIG. 3 with the guide pin and distractor, shownpartially in hidden line, inserted from a lateral approach to thethoracic spine in the disc space.

FIG. 5 is an enlarged front elevational view of the segment of thethoracic spine of FIG. 3 with the distractor, shown partially in hiddenline, inserted from a lateral approach to the thoracic spine and seatedin the disc space and the guide pin removed.

FIG. 6 is a rear perspective view of a segment of the thoracic spinehaving a distractor inserted from a lateral approach to the thoracicspine and seated in the disc space and the extended outer sleeve of thepresent invention coupled to a driver cap and about to be placed overthe distractor.

FIG. 7 is an enlarged front elevational view of the segment of thethoracic spine of FIG. 3 with the distractor and the extended outersleeve inserted from a lateral approach to the thoracic spine and seatedin the disc space.

FIG. 7A is side perspective view of the extended outer sleeve of thepresent invention.

FIG. 8 is a rear perspective view of a portion of the thoracic spinewith the extended outer sleeve fully seated over the distractor insertedfrom a lateral approach to the thoracic spine and seated in the discspace and with the driver cap removed.

FIG. 9 is a front elevational view of a segment of the thoracic spine ofFIG. 3 with the extended outer sleeve inserted from a lateral approachto the thoracic spine and seated in the disc space and engaging theadjacent vertebrae showing the distractor being removed by a distractorpuller.

FIG. 10 is an enlarged front elevational view of the segment of thethoracic spine of FIG. 3 with the extended outer sleeve inserted from alateral approach to the thoracic spine and seated in the disc space andengaging the two adjacent vertebrae.

FIG. 11 is a front elevational view of a segment of the thoracic spineof FIG. 3 with the inner sleeve of the present invention being insertedinto the extended outer sleeve.

FIG. 12 is an enlarged front elevational view of the segment of thethoracic spine of FIG. 3 with the inner sleeve, shown in partial hiddenline, inserted into the extended outer sleeve that is inserted from alateral approach to the thoracic spine in the disc space and engages twoadjacent vertebrae.

FIG. 13 is a side elevational view of a segment of the thoracic spine ofFIG. 3 showing the extended outer sleeve inserted from a lateralapproach to the thoracic spine in the disc space and engaging the twoadjacent vertebrae with the inner sleeve and drill shown in an explodedview and partially in hidden line.

FIG. 14 is a cross sectional view along lines 14-14 of FIG. 13 of thedrill, inner sleeve and extended outer sleeve.

FIG. 15 is a cross sectional view along lines 15-15 of FIG. 13 of thecollar for limiting the drilling depth of the drill.

FIG. 16 is an enlarged front elevational view of the segment of thethoracic spine of FIG. 3 showing the extended outer sleeve inserted froma lateral approach to the thoracic spine and seated in the disc spaceand engaging the two adjacent vertebrae, the inner sleeve inserted inthe extended outer sleeve, and the drill passing through the innersleeve to create a hole across the disc space and into the adjacentvertebrae.

FIG. 17 is an enlarged front elevational view of the segment of thethoracic spine of FIG. 3 with the extended outer sleeve inserted from alateral approach to the thoracic spine and seated in the disc space andengaging the two adjacent vertebrae illustrating a hole drilled acrossthe disc space and into the adjacent vertebrae.

FIG. 18 is a front elevational view of the segment of the thoracic spineof FIG. 3 showing the extended outer sleeve inserted from a lateralapproach to the thoracic spine and seated in the disc space and engagingthe two adjacent vertebrae, an implant driver, and a spinal implantabout to be inserted through the extended outer sleeve and into the holedrilled across the disc space and into the adjacent vertebrae.

FIG. 19 is a front elevational view of the segment of the thoracic spineof FIG. 3 showing the extended outer sleeve inserted from a lateralapproach to the thoracic spine and seated in the disc space and engagingthe two adjacent vertebrae and a spinal implant implanted in the holedrilled across the disc space and into two adjacent vertebrae.

FIG. 20 is a front elevational view of the segment of the thoracic spineof FIG. 3 showing the extended outer sleeve inserted from a lateralapproach to the thoracic spine and seated in the disc space and engagingthe two adjacent vertebrae and an extractor cap for removing theextended outer sleeve about to be coupled to the extended outer sleeve.

FIG. 21 is an enlarged partial sectional view of the extractor capengaging the extended outer sleeve.

FIG. 22 is a front elevational view of the segment of the thoracic spineof FIG. 20 with the distractor puller coupled to the extractor cap shownremoving the outer sleeve from the disc space and the adjacent vertebraein the direction of the arrow.

FIG. 23 is an enlarged front elevational view of a segment of thethoracic spine having a portion of the top vertebrae removed and aportion of the disc space removed and a spinal implant implanted from alateral approach to the thoracic spine in the hole drilled across thedisc space and into the two adjacent vertebrae.

FIG. 24 is a front elevational view of a segment of the thoracic spinehaving a spinal implant implanted from a lateral approach to thethoracic spine into a hole drilled across the disc space and into theadjacent vertebrae with a spinal fixation device coupled to the spinalfusion implant and engaging the adjacent vertebrae to lock the spinalimplant in place.

FIG. 25 is a side perspective view of an alternative embodiment of theextended outer sleeve of the present invention having a pair ofextension members and a pair of prongs.

FIG. 26 is a top plan view of the extended outer sleeve of FIG. 25 shownin partial cutaway with an inner sleeve and a drill inserted within itsinterior and placed adjacent to a vertebra of the spine with the majorvessels and the dural sac and spinal nerves proximate to the vertebrashown in cross section.

FIG. 27 is an anterior elevational view of a vertebra of the spine withthe extended outer sleeve of FIG. 25 shown inserted from the lateralapproach and seated in the disc space and engaging the vertebra.

FIG. 28 is a posterior elevational view of a vertebra of the spine withthe extended outer sleeve of FIG. 25 shown inserted from the lateralapproach of the spine and seated in the disc space and engaging thevertebra.

FIG. 29 is a side elevational view of a segment of the lumbar spine witha first spinal implant inserted from the lateral aspect into a holedrilled across a first disc space and into two adjacent vertebrae, and asecond spinal implant inserted from the lateral aspect into a secondhole drilled across a second disc space and into two adjacent vertebrae.

FIG. 30 is top sectional view along lines 30-30 of FIG. 29 showing thearea of contact of the first spinal implant and the vertebra.

FIG. 30A is a top sectional view similar to FIG. 30 showing the area ofcontact of a spinal implant inserted from slightly anterior(anterolateral) along the lateral aspect of the spine and oriented atleast partially from side to side with respect to the vertebra.

FIG. 31 is an anterior elevational view of a segment of the lumbar spinewith spinal cylindrical implants inserted from the anterior of the spineinto holes drilled across the same disc space and into two adjacentvertebrae.

FIG. 32 is a top sectional view along lines 31-31 of FIG. 31 showing thearea of contact of the two spinal implants and the vertebra which is thesame size as the vertebra of FIG. 30.

FIG. 33 is a top sectional view of a single implant having a diameterequal to the diameter of the implant of FIG. 30 showing the area ofcontact with the vertebra which is the same size as the vertebra of FIG.30.

FIG. 34 is a side elevational view of a segment of the spinal columnwith two spinal implants inserted from front to back at adjacent disclevels between three vertebrae.

FIG. 35 is a perspective side view of an alternative embodiment of theextended outer sleeve of the present invention having a removable distalend with a single extension member and a pair of prongs.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1, a rear perspective view of a segment of thethoracic spine S is shown with a guide pin 30 about to be inserted froma lateral approach (through the lateral chest wall) to the thoracicspine S into the disc space D between two adjacent vertebrae, forexample vertebrae T₇ and T₈. The guide pin 30 may first be used asradiological marker to confirm the correct disk level and instrumentposition, and then functions to align and guide the insertion of theinstrumentation described below into the disc space D. The guide pin 30is inserted through a small incision on the side of a patient's chestcavity perpendicular to the lateral aspect of the vertebrae T₇ and T₈ ofthe thoracic spine S. The guide pin 30 is made of a material appropriatefor surgical use and comprises a shaft portion 40, a tip 50 which may bepointed to facilitate insertion into the disc space D, and a distal end60. In the preferred embodiment, the guide pin has a diameter in therange of 1.5 mm to 5.0 mm, with 2.5 mm being the preferred diameter, anda length in the range of 200 mm to 800 mm, with 350 mm being thepreferred length.

Referring to FIGS. 2 and 3, the guide pin 30 is shown inserted from alateral approach to the thoracic spine S and into the disc space Dbetween adjacent vertebrae T₇ and T₈, with a substantial part of theshaft portion 40 of the guide pin 30 remaining external to the discspace D and functions as a guide post. The tip 50 of the guide pin 30may penetrate the disc space D for a substantial part of the transversewidth W of the vertebrae T₇ and T₈ such that at least a part of theshaft portion 40 is within the disc space D. The guide pin 30 is firmlyembedded in the discal material present within the disc space D, butdoes not protrude through the opposite side of the disc space D toprevent any unwanted damage to that area. The guide pin 30 is placed inthe disc space D so that it is parallel to the end plates of thevertebrae T₇ and T₈, and centered within the disc space D to bisect thedisc space D along the transverse width W of the vertebrae T₇ and T₈. Inthis manner, a substantial portion of the vertebrae T₇ and T₈ is presentnear the circumference of the guide pin 30 such that instruments havinga diameter greater than the guide pin 30 may be inserted into thevertebrae T₇ and T₈ coaxial to the guide pin 30 without protruding fromthe vertebrae T₇ and T₈. Such instruments are guided and aligned duringinsertion by the guide pin 30 so that they are correctly oriented withrespect to the vertebrae T₈ and T₈. The surgeon may monitor the correctorientation of the guide pin 30 within the disc space D indirectly withan image intensifier, or directly with a thorascope if one is beingused.

Once inserted in the disc space D, the guide pin 30 functions as a guidepost for a distractor 100 which is placed over the guide pin 30 andinserted in the disc space D to distract the disc space D and align theadjacent vertebrae T₇ and T₈ by urging them apart. Circumstancespermitting, the surgeon may elect to bypass the use of the guide pin 30and insert the distractor 100 directly. The distractor 100 has acylindrical barrel 106 that terminates at one end in a reduced diameterdisc penetrating portion 102 that is essentially cylindrical, with afurther reduced diameter, bullet-shaped front end 103 to facilitateinsertion into the disc space D. The distractor 100 has a shoulderportion 104 where the penetrating portion 102 extends from barrel 106and has a hollow longitudinal passageway 107 extending the entire lengthof the distractor 100 for receiving the guide pin 30. The passageway 107of the distractor 100 is open at both ends of the distractor 100 and hasa diameter that is slightly greater than the diameter of the shaftportion 40 of guide pin 30. The shaft portion 40 of the guide pin 30 maypass through the passageway 107 as the distractor 100 is placedcoaxially over the guide pin 30. In this manner, the distractor 100 canbe guided and aligned by the guide pin 30 so that it is inserted intothe disc space D coaxial to the guide pin 30 and is properly alignedwith respect to the vertebrae T₇ and T₈. Once the distractor 100 isproperly placed within the disc space D, the guide pin 30 may be removedfrom the disc space D through the passageway 107 of the distractor 100.

The appropriate placement of distractor 100 in the disc space D may bedetermined visually by the surgeon by the use of a thorascope and or bythe use of radiographic, fluoroscopic, or similar procedures, such asutilizing an image intensifier, all of which allow the surgeon todetermine the correct orientation and placement of the guide pin 30 anddistractor 100 within the disc space D. The correct orientation andplacement of the distractor 100 is important to the success of themethod of the present invention, as the purpose of the distractor 100 isto space part and align the vertebrae T₇ and T₈ and to guide theinsertion into the disc space D of the extended outer sleeve 140described in detail below. As the diameter of the distractor 100 isalmost the same as the inner diameter of the extended outer sleeve 140and is the same as the spinal implant I, also described in detail below,the surgeon can use x-rays to determine whether the distractor 100 isproperly oriented with respect to the adjacent vertebrae T₇ and T₈, suchthat any subsequent drilling through the extended outer sleeve 140 andinsertion of spinal implant I will be correctly oriented with respect tothe vertebrae T₇ and T₈. Such a precaution will permit the surgeon tocorrect any misplacement of the distractor 100 before any irreversibledrilling or implant insertion has occurred.

The penetrating portion 102 of the distractor 100 may be of variousdiameters and lengths, the preferred length being less than the knowntransverse width W (side to side) of the vertebrae T₇ and T₈. Thiscombined with the circumferential shoulder portion 104 of the distractor100, which is too large to fit within the disc space D, protects againstthe danger of overpenetration. The barrel 106 of the distractor 100 mayhave at its distal end a recessed portion 108 below the crown 110 whichallows for the distractor 100 to be engaged by an extractor unit shownin FIG. 9.

In the preferred embodiment of the distractor 100, the barrel 106 has adiameter in the range of 10 mm to 30 mm, with 20 mm being the preferreddiameter, and the penetrating portion 102 has a diameter in the range of3 mm to 10 mm, with 6 mm being the preferred diameter.

Referring to FIGS. 4 and 5, once the distractor 100 is inserted into thedisc space D, the penetrating portion 102 of the distractor 100distracts the vertebrae T₇ and T₈ apart, such that the vertebrae T₇ andT₈ to either side of the penetrating portion 102 are forced into fullcongruence and thus become parallel, not only to the penetrating portion102, but to each other. Because of the forced opposition of thevertebrae T₇ and T₈ to the penetrating portion 102 the distractor 100will then come to lie absolutely perpendicular to the plane P of thelateral aspect of the thoracic spine S and absolutely parallel to thevertebral endplates, allowing optimal alignment for the procedure to beperformed.

Referring to FIGS. 6, 7 and 7A, the distractor 100 now serves as both acentering post and an alignment rod for the extended outer sleeve 140which is fitted over the distractor 100 and inserted into the disc spaceD. As shown in FIG. 7A, the extended outer sleeve 140 is a hollowtubular member made of material appropriate for surgical use andpreferably metal, and has an inner diameter sufficiently sized toreceive the distractor 100. The inner diameter of the extended outersleeve 140 closely matches the outer diameter of the distractor 100, sothat a close fit is achieved and the extended outer sleeve 140 isprecisely guided by the distractor 100. The extended outer sleeve 140has at its distal end 146 an extension member 148 and two prongs 149 and150 sufficiently spaced apart to penetrate and hold fixed the twoadjacent vertebrae T₇ and T₈. The extension member 148 is essentially acontinuation of the extended outer sleeve 140 and the prongs 149 and 150are offset from the extended outer sleeve 140 or can also be acontinuation of the extended outer sleeve 140 like extension member 148.The prongs 149 and 150 may have sharp insertion edges 152 and 154 tofacilitate insertion into the vertebrae T₇ and T₈.

Where the surgery is for a disc herniation, the extension member 148 ofthe extended outer sleeve 140 located anteriorly is used without asecond extension member posteriorly, as the use of the two prongs 149and 150 in conjunction with the anterior extension member 148 makes itpossible to operate through the extended outer sleeve 140 posteriorly,without obstruction and with good visibility when an endoscope is usedsuch that any remaining disc herniation may be removed. The extensionmember 148 of the extended outer sleeve 140 provides a protectivebarrier to the structures lying beyond it.

However, if the surgery is not for a disc herniation, but for example,for stabilization of the spine, then the extended outer sleeve may haveboth an anterior extension member 148 and a corresponding posteriorextension member with or without prongs, such as the extended outersleeve 1100 shown in FIG. 35 and described in greater detail below.

In the preferred embodiment, the extension member 148 of the extendedouter sleeve 140 functions to maintain the distraction and alignment ofthe vertebrae T₇ and T₈, as the extension member 148 is being insertedfrom the lateral aspect of the thoracic spine S. Without the extensionmember 148, in order to maintain the proper distraction of the adjacentvertebrae T₇ and T₈, it would be necessary to place a surgicalinstrument, such as a second distractor (not shown) on the opposite sideof the vertebrae T₇ and T₈. This would require a second incision in theopposite side of the patient's chest cavity for insertion of therequired surgical instruments. Further, as it is desired to insert animplant of the maximum possible length across the transverse width W ofthe vertebrae T₇ and T₈, the presence of any instrumentation at theopposite end of the vertebrae T₇ and T₈, would interfere with theinsertion of such an implant. For example, the second distractor on theopposite side of the vertebrae T₇ and T₈, would be in the way of a drillused to create a hole across the transverse width W of the vertebrae T₇and T₈, since the drilled opening would overlap the second distractor.Therefore, the extension member 148 solves the problem of maintaining aneven distraction of the two adjacent vertebrae T₇ and T₈ across theirtransverse width W from only one side of the thoracic spine S, allowingfor the unimpeded insertion of instruments and/or implants. While in thepreferred embodiment, the extended outer sleeve 140 has an extensionmember 148, it is also possible to have an extended outer sleeve withoutany extension members and instead, having prongs of sufficient lengththat engage the bone of the adjacent vertebrae to maintain thedistraction and alignment of the adjacent vertebrae created by thedistractor 100. However, the use of such an extended outer sleevecapable of holding, but not of obtaining, the desired intervertebraldistraction and alignment would require the use of a distractor prior toits insertion as earlier described herein.

In the preferred embodiment of the extended outer sleeve 140, a singleextension member 148 is present and oriented anteriorly to protect themajor vessels located to the anterior aspect of the thoracic spine S.The extended outer sleeve 140 has no extension member near the posterioraspect the spine as it is often necessary to access the spinal canal inorder to remove any diseased discal material. In the specialcircumstances where only vertebral fusion is desired, the extended outersleeve 140 may have a second extension member (not shown) identical tothe extension member 148 positioned diametrically opposite the extensionmember 148 in order to protect the spinal canal, and in such instancemay or may not have the bone penetrating prongs 149 and 150.

The extension member 148 of the extended outer sleeve 140 has a heightthat is generally approximately equal to the diameter of the penetratingportion 102 of the distractor 100, such that the extension member 148 iscapable of maintaining the spacing created by the insertion of thedistractor 100 between the adjacent vertebrae T₇ and T₈ which isgenerally the restoration to normal of the disc space D. The extensionmember 148 is tapered at its leading edge 151 to facilitate insertioninto the disc space D and is positioned approximately 120 degrees fromeach of the two prongs 149 and 150. The extension member 148 of theextended outer sleeve 140 works in conjunction with the prongs 149 and150 which engage the vertebrae T₇ and T₈, respectively, to maintain thedistraction and alignment of the vertebrae T₇ and T₈. Further, theprongs 149 and 150 not only hold the vertebrae T₇ and T₈ apart, butduring drilling also help to hold them together so as to resist themmoving apart.

In the preferred embodiment, the extension member 148 of the extendedouter sleeve 140 has a length that is less than the transverse width Wof the vertebrae T₇ and T₈. The extension member 148 needs to berelatively long because it must maintain distraction of the adjacentvertebrae T₇ and T₈ when placed across the transverse width W of thevertebrae T₇ and T₈. Therefore, if the extension member 148 is shorterthan one half the transverse width W of the vertebrae T₇ and T₈, it maynot be capable of distracting and aligning the vertebrae T₇ and T₈, anda second distractor would be required as described above, to achieve thecorrect distraction and alignment of the vertebrae T₇ and T₈.

In the preferred embodiment, the extended outer sleeve 140 has an outerdiameter in the range of 12 mm to 34 mm, with 24 mm being the preferredouter diameter, and an inner diameter in the range of 10 mm to 28 mm,with 20 mm being the preferred inner diameter of the extended sleeve140.

In the preferred embodiment, the extension member 148 of the extendedouter sleeve 140 has a length in the range of 14 mm to 30 mm, with 24 mmbeing the preferred length, and a height in the range of 3 mm to 10 mm,with 6 mm being the preferred height. In the preferred embodiment, theprongs 149 and 150 of the extension member 140 have a length in therange of 6 mm to 20 mm, with 14 mm being the preferred length and adiameter in the range of 2 mm to 3 mm, with 2 mm being the preferreddiameter of the prongs 149 and 150.

Referring specifically to FIG. 6, coupled to the proximal end 157 of theextended outer sleeve 140 is a driver cap 160 in the form of animpaction cap which has at its far end a flat, closed-back surface 162and at its other end a broad, circular opening. The driver cap 160 isused for driving the extended outer sleeve 140 toward the vertebrae T₇and T₈ and fits over both the extended outer sleeve 140 and thedistractor 100. An impaction force, such as a mallet blow, is applied tosurface 162 of the driver cap 160 to advance the extended outer sleeve140. That force is transmitted to the extended outer sleeve 140 via itsproximal end 157, seating the prongs 149 and 150 of the extended outersleeve 140 into the vertebrae T₇ and T₈ and inserting the extensionmember 148 into the disc space D. As the extended outer sleeve 140 isadvanced forward, the crown 110 of the distractor 100 is allowed toprotrude within the driver cap 160 unobstructed until it contacts theinterior of the driver cap 160, such that further taps of the malletwill not further advance the extended outer sleeve 140. Any furthermotion is resisted by the flat shoulder portion 104 of the distractor100 abutting the hard lateral outer surfaces of the adjacent vertebraeT₇ and T₈. The flat, planar area 156 of the distal end 146 of extendedouter sleeve 140 serves to resist the further insertion of the extensionmember 148 into the disc space D and to resist further insertion of theprongs 149 and 150 into the vertebrae T₇ and T₈. In this way, theextended outer sleeve 140 is safely and assuredly inserted to itsoptimal depth, and no further, and rigidly secures the two adjacentvertebrae T₇ and T₈ as shown in FIG. 7.

Referring to FIGS. 8 and 9, the driver cap 160 is then removed and thecrown 110 and the recessed portion 108 of the distractor 100 protrudefrom the proximal end 157 of the extended outer sleeve 140. Thedistractor 100 may now be removed from within the extended outer sleeve140 since the extended outer sleeve 140 functions to maintain thedistraction and alignment of the vertebrae T₇ and T₈. The extended outersleeve 140 is held secure by the extension member 148 inserted withinthe disc space D and by the prongs 149 and 150 engaging the vertebrae T₇and T₈.

A distractor puller 200 is utilized to remove the distractor 100 in thedirection of arrow Y from within the disc space D leaving the extendedouter sleeve 140 in place. The distractor puller 200 has front portion202, a mid portion 204, and a back handle portion 206. The front portion202 of the distractor puller 200, is connected to one end of shaft 210which at its far end is connected to the back handle portion 206. Thedistractor puller 200 is described in detail in copending applicationSer. No. 08/074,781, now U.S. Pat. No. 5,484,437 entitled APPARATUS ANDMETHOD FOR INSERTING SPINAL IMPLANT, and is incorporated herein byreference. The socket-like front portion 202 of the distractor puller200 engages the circumferential recessed portion 108 of the distractor100.

A cylindrical and freely movable weight 216 is fitted around shaft 210between the front portion 202 and the rear handle portion 206 of thedistractor puller 200 so as to form a slap hammer. The weight 216 of thedistractor puller 200 is gently and repeatedly slid along the shaft 210and driven rearwardly against flat surface 228 of the rear handleportion 206 to transmit a rearward vector force to front portion 202 andto the distractor 100 to which it is engaged. In this manner, thedistractor 100 is removed from within the disc space D and out of theextended outer sleeve 140 without disturbing it.

Referring to FIG. 10, once the distractor 100 has been completelyremoved from within the extended outer sleeve 140 and from within thedisc space D, the extension member 148 remains within the disc space Dand the prongs 149 and 150 rigidly maintain the appropriate distractionand the relative position of the adjacent vertebrae T₇ and T₈. Theremainder of the procedure occurs entirely through the extended outersleeve 140 and the space therein is sealed off from any of the organs ofthe chest.

Referring to FIGS. 11 and 12, since the extended outer sleeve 140 is ofa fixed length and rigid, the flat rearward surface 172 of the distalend 146 may be used as a stop to the advancement of any instrumentsplaced through the extended outer sleeve 140, thus protecting againstaccidental overpenetration. Further, the extended outer sleeve 140assures that the further procedure to be performed will occur coaxial tothe disc space D and further, be symmetrical in regard to each of theadjacent vertebrae T₇ and T₈.

Where it is desirable to drill a hole smaller in diameter than thespinal implant to be inserted, such as in the case where the spinalimplant is threaded, an inner sleeve 242 which functions as a drillguide and spacer having a thickness which corresponds to the differencebetween the major and minor diameters of the spinal implant, is insertedin the proximal end 158 of the extended outer sleeve 140. The innersleeve 242 is a hollow tubular member comprising a barrel portion 243and a cuff portion 244 having a greater outer diameter than the barrelportion 243. The cuff portion 244 of the inner sleeve 242 seats againstthe flat rearward surface 172 of the extended outer sleeve 140 toprevent further insertion of the inner sleeve 242. The distal end 246 ofthe inner sleeve 242 extends towards but does not impact the lateralaspect of the adjacent vertebrae T₇ and T₈ in the interior of theextended outer sleeve 140 when fully seated. The barrel portion 243 ofthe inner sleeve 242 has an outer diameter that fits within the innerdiameter of the extended outer sleeve 140. In the preferred embodiment,the barrel portion 243 of the inner sleeve 242 has an outside diameterin the range of 10 mm to 28 mm, with 20 mm being the preferred outerdiameter, and a wall thickness in the range of 0.5 mm to 3 mm, withapproximately 0.75 to 1.5 mm being the preferred thickness.

Referring to FIGS. 13-15, once the inner sleeve 242 is seated within theextended outer sleeve 140, a drill 250 connected to a handle 260 or to adrill motor (not shown), is introduced through the aperture in theproximal end 248 of the inner sleeve 242 and utilized to create a holeacross the disc space D and into the adjacent vertebrae T₇ and T₈. Thedrill 250 reams out arcs of bone which it engages from the adjacentvertebrae T₇ and T₈, as well as any discal material within its path downto its predetermined and limited depth. It is appreciated that if aninner sleeve 242 is not used, the drill 250 may be placed directly intothe extended outer sleeve 140 to create a hole across the disc space Dand into the adjacent vertebrae T₇ and T₈.

The drill shaft of drill 250 comprises an upper portion 252, a centralrecessed portion 254 of a smaller diameter and a lower cutting portion256. The drill 250 has a narrow engagement portion 258, which allows itto be affixed to a driving mechanism which may be either a manual unitsuch as, handle 260, or a power unit such as an electric drill motor.The upper portion 252 has a plurality of grooves 261 for engaging acircumferential collar 262 of an increased diameter which serves tolimit the depth of penetration of the drill 250 and may be fixed, orlockably adjustable.

Referring to FIG. 15, a cross sectional view of the circumferentialcollar 262 is shown engaging the upper portion 252 of the shaft of drill250. The collar 262 comprises diametrically opposite first and secondflanges 264 and 266. The first and second flanges 264 and 266 arepivotably attached to the collar 262 by first and second pins 268 and270 and spring biased by first and second spring 272 and 274. The firstand second flanges 264 and 266 of the collar 262 are contoured tocorrespond to the curvature of the upper portion 252 of the drill 250.The first and second flanges 264 and 266 engage one of the grooves 261when in the full biased position as shown in FIG. 15. To disengage thegrooves 261, the first and second 264 and 266 are compressed together bythe surgeon such that the first and second springs 272 and 274 arecompressed and the first and second flanges 264 and 266 pivot away fromthe upper portion 252 of the shaft, such that the collar 262 can slidealong the upper portion 252 of the drill 250. The first and secondflanges 264 and 266 of the collar 262 are oriented opposite each otherand need to be compressed together in order to disengage the grooves261. The compression of one of the flanges 264 and 266 alone will notdisengage the collar 262 from the grooves 261. In this manner, collar262 can not become accidentally disengaged during the rotation of thedrill 250.

While it is believed that this mechanism is entirely novel, it isappreciated that various mechanisms to lockably adjust drills arewell-known to those skilled in the art. Such mechanisms include, but arenot limited to, the use of collets, threaded shafts with lock nuts, andflanges engaging grooves forced therein by either a cap pulled over theflanges or screwed down upon them.

Referring to FIGS. 13 and 14, in the preferred embodiment, the forwardcutting edge 280 of drill 250 is a four cutting edge end millmodification of a large fluted drill design. The cutting portion 256 ofthe drill 250 resembles an end cutting mill which may contain anyworkable number of cutting surfaces, but preferably four or more, thatare relatively shallow such that the advancement of the drill 250 occursmore slowly. The cutting portion 256 of the drill 250 may be of adifferent diameter depending on the type of spinal implant that is beinginserted. If the spinal implant being inserted is threaded, the outsidediameter of the cutting portion 256 of the drill 250 would generallycorrespond to the minor diameter of the threaded implant. The innersleeve 242 has an inner diameter slightly greater than the minordiameter of a threaded implant and its outer diameter is slightlysmaller than the inside diameter of the extended outer sleeve 140 whichhas the same outer diameter as the major diameter (with threads) of thethreaded implant. If the implant is not threaded, the outside diameterof the drill 250 corresponds to the inside diameter of the extendedouter sleeve 140 such that a hole the maximum diameter of the extendedouter sleeve may be drilled.

The inner sleeve 242 serves many functions. First, it provides anintimate drill guide for drill 250 in the event a smaller diameter holeis to be drilled than that of the inside diameter of the extended outersleeve 140. Second, since the inner sleeve 242 guides the drill 250, itallows for the extended outer sleeve 140 to have an internal diameterlarge enough to admit a threaded implant, which is larger in diameterthan the outer diameter of the drill 240.

If a larger extended outer sleeve 140 were utilized absent the innersleeve 242, then the drill 250 would be free to wander within theconfines of that greater space and would not reliably make parallel cutsremoving equal portions of bone from the adjacent vertebrae T₇ and T₈.Further, the bone removal not only needs to be equal, but must becorrectly oriented in three dimensions. That is, the path of the drill250 must be equally centered within the disc space, parallel theendplates, and perpendicular to the long axis of the spine dissectingthe disc space D.

A further purpose of the inner sleeve 242 is that it may be removedsimultaneously with the drill 250, thereby trapping the debris, bothcartilaginous and bony, generated during the drilling procedure. Thedebris is guided rearward by the large flutes 251 of the lower cuttingportion 256 and is collected around the central recessed portion 254 andthen contained and between the recessed portion 254 and the inner wallof the inner sleeve 242. Thus, by removing the drill 250 in conjunctionwith the inner sleeve 242, much of the debris generated by the drillingprocedure is safely removed from the drilling site.

Referring to FIG. 17, once the drill 250 and the inner sleeve 242 areremoved from the extended outer sleeve 140 a cylindrical hole 290remains across the disc space D and into the two adjacent vertebrae T₇and T₈. The cylindrical hole 290 is oriented across the transverse widthW of the vertebrae T₇ and T₈ in which an implant of appropriate diameteris to be implanted. The proper distraction and orientation of the twoadjacent vertebrae T₇ and T₈ is maintained by the extension member 148and the prongs 149 and 150 of the extended outer sleeve 140.

The cylindrical hole 290 may then be irrigated and vacuumed through theextended outer sleeve 140 to remove any remaining debris from thedrilling. If necessary, a thrombin soaked sponge may be inserted throughthe extended outer sleeve 140 and into the cylindrical hole 290 tocoagulate any bleeding. The thrombin soaked sponge is then removed andthe surgeon utilizing an endoscope then visually inspects thecylindrical hole 290 for any remaining discal material, and removes anysuch material requiring such removal with a surgical instrument such asa curette or rongeur.

Referring to FIG. 18, with the extended outer sleeve 140 still in place,the surgical site is now fully prepared to receive a spinal implant Ifor fusion of the vertebrae T₇ and T₈. The spinal implant I may becoated with, and/or made of, and/or loaded with substances consistentwith bony fusion which may promote bone growth and/or fusion prior tobeing implanted. Once the spinal implant I has been prepared forimplantation, a driver instrument, such as driver 300 may be used toeither insert or to remove spinal implant I. Driver 300 has at itsdistal end 302, a rectangular protrusion 304, which intimately engagesthe complimentary rectangular slot in the rear of implant I. Extendingfrom the rectangular protrusion 304 is threaded portion 306, whichextends as a rod through hollow shaft 308 and hollow barrel portion 310to knob 312 where it can be rotationally controlled. Threaded portion306 screws into a threaded aperture in the spinal implant I and bindingthem together such that driver 300 can be rotated via paired anddiametrically opposed extending arms 314 and 316 and in either directionwhile maintaining contact with the spinal implant I.

Affixed to the driver 300, the spinal implant I is then introducedthrough the extended outer sleeve 140 and if the spinal implant I isthreaded, screwed into the cylindrical hole 290 between the twovertebrae T₇ and T₈ until such time as the leading edge of the implantcap 318 reaches the depth of the cylindrical hole 290 at which time itsforward motion is impeded by the bone lying before it which had not beendrilled out. This allows for a progressive feel to the surgeon as thespinal implant I is inserted into place. It is appreciated that if thespinal implant I is not threaded, instead of being screwed into hole290, it may be linearly advanced into hole 290 by pushing the driver 300toward the hole 290.

The terminal resistance to further seating provides significant tactilefeedback to the surgeon. Visual monitoring of the depth of insertion ofthe spinal implant I is provided to the surgeon by observing theprogressive approximation of the forward surface 320, of barrel portion310, as it approaches the rearward facing surface 172 of extended outersleeve 140 and/or by the use of an image intensifier. As a final safetymechanism, when the full depth of insertion has been achieved, forwardsurface 320 of instrument 350 will abut surface 172 of the extendedouter sleeve 140, prohibiting any further installation of the implant.Once the spinal implant I has been fully installed, the driver 300 isdissociated from the implant by turning knob 312 in a counterclockwisedirection. The driver 300 is then withdrawn from the extended outersleeve 140.

Referring to FIG. 19, the spinal implant I is shown fully installed tothe determined depth in the cylindrical hole 290 drilled across the discspace D and into the adjacent vertebrae T₇ and T₈. The spinal implant Ishown comprises a hollow tubular member which in the preferredembodiment is made of an ASTM surgically implantable material,preferably titanium. However, it is appreciated that other implants,cylindrical or partially cylindrical, or of a variety of shapes, andwith or without threads or surface roughenings may be used with theinstrumentation and method of the present invention.

Referring to FIGS. 20 and 21, an extractor cap 340 for removing theextended outer sleeve 140 is shown about to be coupled to the extendedouter sleeve 140. The extractor cap 340 engages the proximal end 157 ofthe extended outer sleeve 140 by spring tabs 342 a and 342 b on eitherside of extractor cap 340 which snap-fit into openings 344 a and 344 bon either side of the extended outer sleeve 140 to lock in place. Theextractor cap 340 has a top 346 that is similar in structure to theproximal end of the distractor 100, having a recess portion 350 and acrown portion 352.

Referring to FIG. 22, once the extractor cap 340 is coupled to theextended outer sleeve 140, the distractor puller 200 is coupled to thetop 346 of extractor cap 340 to remove the extended outer sleeve 140from the disc space D and from the adjacent vertebrae T₇ and T₈ in thedirection of the arrow Z.

Referring to FIG. 23, once the extended outer sleeve 140 has beenremoved, the spinal implant I remains implanted within the cylindricalhole 290 drilled across the disc space D and the implant engages the twoadjacent vertebrae T₇ and T₈.

Referring to FIG. 24, the spinal implant I may be further stabilizedwith use of a spinal fixation device 400 such as the staple disclosed incopending application Ser. No. 08/219,626 entitled APPARATUS,INSTRUMENTATION AND METHOD FOR SPINAL FIXATION, which is incorporatedherein by reference. The spinal fixation device 400 is coupled to thespinal implant I with a locking screw 410 and engages the vertebrae T₇and T₈ via prongs 420 and 422. The spinal fixation device 400 functionsto stabilize the spinal implant I and prevent any unwanted excursion ofthe spinal implant I during the spinal fusion process. It is appreciatedthat prior to removal of the extended outer sleeve 140, a centering post(not shown) may be inserted through the extended outer sleeve 140 andattached to the threaded opening in the back of the spinal implant I.The extended outer sleeve 140 is then removed and the centering postfunctions as guide to align the spinal fixation device 400 as it isbeing driven into the vertebrae T₇ and T₈ as described in detail in thecopending application referenced immediately above.

In the above description in regard to the thoracic spine, the surgicalprocedure has been described as being performed through a hollow tube(extended outer sleeve 140) and with the aid of a thorascope. It isappreciated that there may be circumstances where the surgeon will electto perform the surgical procedure through an incision, such as athoracotomy, where direct visualization of the surgical site is possibleobviating the need for the thorascope but without diminishing theteaching of the method of the present invention. In such cases, amodification of the extended outer sleeve 140, such as the extendedouter sleeve 1100 shown in FIG. 35 and described in detail below, havinga detachable distal end may be beneficially utilized by the surgeon. Inthis manner, the surgeon has direct visualization of the surgical sitewhile the proper distraction and alignment of the adjacent vertebrae ismaintained throughout the procedure by the distal end of the extendedouter sleeve.

While the present invention has been described in association with theinsertion of a threaded spinal implant, it is recognized that otherforms of implants may be used with the present method. For example,dowels, made from bone, coral or artificial materials, knurled orirregularly shaped cylinders or spheres, partial cylinders or any othershaped implants that can be introduced through the extended outer sleeve140, which itself need not be cylindrical may be used.

When such implants are used, it is appreciated that the steps of themethod of the present invention described above may be reduced. Forexample, once the extended outer sleeve 140 has been seated such thatthe extension portion 148 is inserted in the disc space D and the prongs149 and 150 engage the adjacent vertebrae, the step of inserting theinner sleeve 242 may be omitted and a drill having a diameterapproximating that of the inner diameter of the extended outer sleeve140 may be used to drill a hole the size of the inner diameter of theextended outer sleeve 140 across the disc space D and into the adjacentvertebrae. Once the drill has been removed, any remaining discalmaterial or debris may be removed by irrigating and vacuuming the hole,and an implant such as a bone dowel or an implant without threads, maybe linearly advanced through the extended outer sleeve 140 and implantedinto the hole. The extended outer sleeve 140 is then removed in the samemanner described above. Where the implant shape is generally notcircular, an appropriately shaped chisel may be used by itself or inconjunction with a drill to prepare an opening for the fusion implantthat is other than round.

It is further appreciated that it is also within the scope of thepresent invention to provide a method and instrumentation for theinsertion of a spinal implant into the disc space between two adjacentvertebrae, without the drilling away of significant bone from thevertebrae. Such implants may have a height corresponding to the heightof a disc space D and may be pushed into the disc space D whendistracted once the disc space D has been cleaned out. This type ofimplant would preferably have in part a rectangular cross section and anextended outer sleeve used for the insertion of such implants would havea corresponding cross section and shape. Further, it is appreciated thatthe extended outer sleeve and inner sleeve of the present invention mayhave any shape or size corresponding to the shape and size of theimplant to be inserted without departing from the scope of the presentinvention.

While the above description has been directed to the thoracic spine, themethod and instrumentation of the present invention may also be utilizedin the lumbar spine. In the preferred method, the surgeon makes a smallincision in the abdominal wall and gently dissects his wayretroperitoneal to reach the lateral aspect of the spine. As with thethorascopic method described above, the surgeon may use an endoscopewithin and/or outside of the extended outer sleeve to facilitate thesurgery, and thereby require an incision barely larger than the diameterof the extended outer sleeve which itself is not much larger than theimplant.

Referring to FIG. 25, an extended outer sleeve 1000 for use with thelateral method in the lumbar spine is shown. The extended outer sleeve1000 is similar to the extended outer sleeve 140 described above andcomprises a hollow tubular member 1002 having a distal end 1010 which iscontoured to hug the vertebrae, for example L₄ and L₅. The extendedouter sleeve 1000 has anterior and posterior extension members 1020 and1022, each having different heights, that are opposed 180 degrees fromeach other. Also extending from the distal end 1010 may be prongs 1012and 1014, similar to prongs 149 and 150 described above, for engagingthe bone of the adjacent vertebrae L₄ and L₅. The extension members 1020and 1022 are tapered at their leading edges 1024 and 1026 respectively,to facilitate insertion.

As shown in FIGS. 26-28, the extended outer sleeve 1000 is designed tobe used in approaching the lumbar spine laterally from either side ofthe spinal column. The extended outer sleeve 1000 by means of itsextended portions 1020 and 1022 is capable of correcting those spinaldeformities, such as scoliosis or any abnormality of kyphosis orlordosis, occurring specifically from a deformity of the disc. Forexample, in order to restore lordosis in the lumbar spine, the anteriorextension member 1020 is placed anteriorly between the adjacentvertebrae L₄ and L₅ and the posterior extension member 1022, having alesser height than the extension member 1020, is placed posteriorly. Thegreater height of the extension member 1020 relative to the extensionmember 1022 maintains the anterior portions of the vertebrae L₄ and L₅spaced apart at a greater distance than the posterior portions of thevertebrae L₄ and L₅ producing an angular relationship between the bodiesas would exist with naturally occurring physiologic lordosis. Oncerestored, lordosis is maintained throughout the surgical procedure.

Scoliosis refers to an abnormal curving of the spine when viewed fromstraight ahead or behind. Since the extension members 1020 and 1022 maybe of a specific and constant height throughout their entire lengths,both sides of the disc space D are lifted to exactly the same height,thus eliminating any side to side angular deformity occurring throughthat disc space.

Referring specifically to FIG. 26, it can be appreciated that theposterior extension member 1022 effectively prevents any injury to thedural sac and neural elements, while the anterior extension member 1020in a similar fashion, protects the great blood vessels including theaorta, vena cava and the iliac arteries and veins. As the extended outersleeve 1000 of the present invention is quite stable once inserted, thepreferred embodiment is shown as having only two prongs 1012 and 1014,one each to engage each of the adjacent vertebrae L₄ and L₅. It is,however, understood that the extended outer sleeve 1000 may have more orless prongs or none at all. The distal end 1010 of the tubular member1002 is contoured adjacent the origin of the anterior and posteriorextended members 1020 and 1022 so as to assure an intimate fit betweenthe tubular member 1002 and the vertebrae L₄ and L₅ adjacent the discspace D to which it is opposed, and for the purpose of confining thesurgery to within the extended outer sleeve 1000 and excluding theadjacent soft tissues from potential injury. In the preferredembodiment, the distal end of the tubular member 1002 and the anteriorand posterior extended members 1020 and 1022 themselves have beenreinforced, that is are thicker than the adjacent tubular member 1002itself so as to provide for increased support within the lumbar spine.

Referring still to FIG. 26, the extended outer sleeve 1000 engages thespine laterally, although the surgical approach in reaching the spinemay be from an anterior, lateral, or anterior-lateral incision on theoutside of the body, and is hereinafter referred to as the “LateralMethod”. The “Lateral Method” involves the insertion of a distractor,such as, but not limited to the distractor 100 described above into thelateral aspect of the spine, and generally from a side to side directionalthough said direction could be slightly from anterolateral to slightlyposterolateral (diagonalized from the transverse axis) without departingfrom the teaching of the method of the present invention to distract theadjacent vertebrae, in this example, L₄ and L₅. Once the distractor 100is in place, if fusion alone is to be performed, then the extended outersleeve 1000 having both anterior and posterior extension members 1020and 1022 is utilized. The extended outer sleeve 1000 is placed over thedistractor 100 such that the posterior extension member 1022 ispositioned at the posterior aspect of the spine and the anteriorextension member 1020 is positioned at the anterior aspect of the spine.Once the extended outer sleeve 1000 is in place, the distractor 100 isremoved. Alternatively, it is appreciated that the “Lateral Method” maybe performed without the use of a distractor. Instead, the extendedouter sleeve 1000 may be inserted from the lateral aspect of the spinedirectly since the extension members 1020 and 1022 function to distractthe adjacent vertebrae L₄ and L₅ to restore and maintain the normalangular relationship of those vertebrae L₄ and L₅.

If the implant to be inserted has surface irregularities such that thereis a major diameter (including the surface irregularities) and a minordiameter (excluding the surface irregularities), then an inner sleeve1040 similar to the inner sleeve 242 described above, may be insertedinto the extended outer sleeve 1000. The inner sleeve 1040 functions asa drill guide and spacer having a thickness which corresponds to thedifference between the major and minor diameters of such implant asdescribed in detail above in reference to an inner sleeve 1040. A drill250, described above, is inserted into the inner sleeve 1040 and is usedto drill the vertebrae with the inner sleeve 1040 providing a moreintimate fit to the drill 250, than the larger bore of the extendedouter sleeve 1000 could have alone and thus more precisely controllingthe path of the drill 250. The inner sleeve 1040 and the drill 250 maybe removed from the extended outer sleeve 1000 together thus trappingand removing much of the debris produced by the actual drilling. It isappreciated that in the alternative, a drill (not shown) may be usedsuch that the distal bone engaging portion has an outside diametergenerally corresponding to the minor diameter of the implant and moreproximally, a shaft portion with a larger diameter generallycorresponding to the major diameter of the implant. An implant I maythen be inserted according to the method described above. If the implantto be inserted does not have a major and minor diameter, then no innersleeve is required, and the drill 250 having a diameter correspondingwith the diameter of such an implant may be inserted directly intoextended outer sleeve to drill the vertebrae L₄ and L₅.

While not considered the preferred method under most circumstances it isnevertheless anticipated that one could drill the described hole acrossthe disc space and into each of the adjacent vertebrae from the lateralaspect of the spine and in at least a partially side to side directionthrough the extended outer sleeve and then remove the extended outersleeve and insert at least one spinal implant also from the lateralaspect of the spine and in an at least a partially side to sidedirection and with or without the use of some form of spinal distractor.In which circumstance the use of an inner sleeve is of less importancethan that the size of the opening created is sufficient such that it ispossible to insert the implant. To that end and independent of whetherthe extended outer sleeve is left in place for implant insertion, andwhether an inner sleeve is used during drilling it is anticipated andshould be appreciated that the extended outer sleeve and opening may beof a variety of shapes and that the creation of spaces of varied shapesacross a disc and within the spine may be achieved by use of aninstrument appropriate for the surgical removal of spinal material, suchas a chisel or a router, and with or without the use of a drill, and/oran inner sleeve, and/or an extended outer sleeve; and with the essentialelement being that the space within the spine is being created across adisc intermediate two adjacent vertebrae from the lateral aspect of saiddisc and at least in part in a from side to side direction and that animplant is then inserted also from the lateral aspect of said disc whichimplant occupies at least in part said space, engages at least in parteach of the vertebrae adjacent said disc space and comes to lie in an atleast partially side to side direction across said disc space.

Referring to FIGS. 29 and 30, the implants I and J are shown insertedacross the disc spaces D between vertebrae L₃, L₄ and L₅, respectively.FIG. 30 is a top sectional view along lines 30-30 of FIG. 29 showing thearea of contact of the implant I and the vertebrae L₄. It can be seenfrom FIG. 30 that the implant I has a true lateral orientation withrespect to the vertebra L₄, such that there is a great area of contactbetween the implant I and the vertebra L₄.

Referring to FIG. 30A, a top sectional view of a vertebra similar toFIG. 30 is shown illustrating the area of contact of the implant I andthe vertebrae L₄ when the implant I is inserted with the “LateralMethod” of the present invention from a slightly anterior position(anterolateral) along the Lateral aspect of the spine and in an at leastpartially side to side direction.

Referring to FIGS. 31 and 32, illustrating the prior art method, twoimplants 1050 and 1052 are inserted from the anterior or posterioraspect of the spine so that they are oriented in an anterior toposterior direction across the disc space D and vertebrae L₄ and L₅. Itcan be seen that implants 1050 and 1052 must have a much smallerdiameter than implant I to fit within the width of the spine andtherefore have very small areas of engagement to the vertebraethemselves as most of the diameter of the implants is used in justspanning across the height of the disc before contacting said vertebrae.FIG. 32 is a top sectional view along lines 32-32 of FIG. 31 showing thearea of contact of the two spinal implants 1050 and 1052 and thevertebra L₅.

Referring to FIG. 33, a top sectional view showing the area of contactof a cylindrical spinal implant 1090 having the same diameter as implantI shown in FIG. 30, inserted from the anterior to posterior directionacross the vertebra L₅ is shown and seen to have by necessity a muchshorter length.

Referring to FIGS. 30 and 32-33, it can then be appreciated that animplant I inserted from the lateral aspect of the spine may have adiameter almost as great as the depth of the spine from front to back atthat location unlike two implants such as implants 1050 and 1052inserted side by side from front to back or the reverse where eachimplant can have a diameter no greater than one half the width of thespine at that level. It can further be appreciated that while the heightof the disc space itself hardly affects the area of contact of thesingle large implant I with the adjacent vertebrae, it substantiallyeffects the area of contact of the two implants 1050 and 1052 insertedin the front to back directions side by side. Further, as the lumbarvertebrae and discs are much wider from side to side then they are deepfrom front to back, it can be appreciated that when single implants ofthe same diameter are inserted across a given lumbar disc, the laterallyinserted implant I may be of a much greater length and thus have morearea of contact, for stability and fusion than implant 1090 insertedfrom anterior to posterior.

Referring to FIG. 34, a segment of the spinal column having singleimplants 1095 and 1096 inserted from front to back at adjacent disclevels between three vertebrae V₁₋₃ is shown. As it can be seen in FIG.34, it is generally not possible to increase the diameter of singularimplants inserted from front to back without risking severe structuraland vascular damage to that area of the spine. Implants 1095 and 1096each have a diameter that is substantially greater than the diameter ofimplant 1090, such that implants 1095 and 1096 could in theory have agreater area of contact with the adjacent vertebrae than implant 1090.However, in application, as a result of the larger diameter of theimplants 1095 and 1096, a large portion of bone from the adjacentvertebrae would have to be removed to accommodate the large diameter ofeach of the implants 1095 and 1096 which would significantly weaken thestructural integrity of those vertebrae. This is especially a problemwhen as shown in FIG. 34, implants 1095 and 1096 are inserted atadjacent disc levels such that the intermediate vertebrae V₂ would becut in half to form a “butterfly” pattern resulting in the complete lossof the structural integrity of vertebrae V₂.

Thus, the implant I of the present invention inserted laterally providesfor greater surface area of contact, the largest volume of fusionpromoting material, and the greatest mechanical engagement and thusstability, and is therefore an improvement upon other methods of implantinsertion in facilitating a successful fusion.

Referring to FIG. 35, an alternative embodiment of the extended outersleeve is shown and generally referred to by the numeral 1100. As only asingle relatively small incision (approximately three inches or less) isrequired through the abdominal wall of the patient to perform theprocedure for the fusion of two vertebrae adjacent a disc space in thelumbar spine, it is anticipated that the surgeon may prefer to performthe method of the present invention under direct vision, without theneed for an endoscope. In such a circumstance, a convertible extendedouter sleeve 1100 may be used. The convertible extended outer sleeve1100 may be similar in structure to the extended outer sleeve 1000,except that it comprises a hollow tubular member 1102 that isdisengageable from the distal end portion 1104 of the convertibleextended outer sleeve 1100. As shown in FIG. 35 the extended outersleeve 1100 has a detachable hollow tubular member 1102. The vertebraeengaging distal end portion 1104 may be as shown in FIG. 35 or may besimilar to the distal end shown previously in FIG. 7A, such that theconvertible extended outer sleeve 1100 may be useable throughout thespine.

The convertible extended outer sleeve 1100 is inserted in the disc spaceD and the adjacent vertebrae L₄ and L₅ as described above for theextended outer sleeve 1000. Once the extension member 1120 is seated inthe disc space D and the prongs 1112 and 1114 are engaged to thevertebrae L₄ and L₅, the hollow tubular member 1102 may be dissociatedfrom the distal end portion 1104 which remains engaged to the vertebraeL₄ and L₅. In this manner, if an incision is made to access the spinedirectly, the surgeon may access the disc space D through the distal endportion 1104 which is closer to the spine, without having to passthrough the entire length of the convertible extended outer sleeve 1100.With the distal end portion 1104 in place, the vertebrae remaindistracted and aligned, and since the hollow tubular member 1102 hasbeen removed, it is then possible for the surgeon to work in and aroundthe spine under direct vision. The shortened distal end portion 1104 ofthe convertible extended outer sleeve 1100 left protruding from theadjacent vertebrae may be selected to be of a length such that it stillserves to offer some protection to the large blood vessels which aresafely positioned outside of the remaining working channel.Alternatively it can be of any length so as to fulfill the surgeon'spurposes. The hollow tubular member 1102 may be re-engaged to the distalend portion 1104 for inserting an implant I in the manner describedabove.

In the specific embodiment of the convertible extended outer sleeve1100, the distal end portion 1104 has a single extension member 1120 andtwo prongs 1112 and 1114 positioned approximately 120 degrees from theextension member 1120 for engaging the two adjacent vertebrae L₄ and L₅,for the purpose of allowing the surgeon direct access to the spinalcanal. Thus, if a discectomy is to be performed, an extended outersleeve having a single anterior intradiscal extended member 1120, butwithout a posterior extended member, and with two vertebrae engagingprongs 1112 and 1114 may be used.

It is appreciated that for surgery on the thoracic spine, while themethod described above wherein the entire procedure is performed throughthe extended outer sleeve 140 is preferred, it is also possible toutilize the convertible extended outer sleeve 1100 when a fullthoracotomy is made to access the thoracic spine without having to workthrough the entire length of the extended outer sleeve. In this mannerthe surgeon may directly visualize and access the surgical site.

Further, combining the features of the absence of any posteriorintradiscal extended member with the convertible extended outer sleeve1100 permits easy and direct access to the spinal canal for removal ofany diseased discal material.

While the present invention has been described in detail with regards tothe preferred embodiments, it is appreciated that other variations ofthe present invention may be devised which do not depart from theinventive concept of the present invention.

1. A spinal distractor for use in spinal fusion surgery within an adulthuman thoracic and lumbar spine for positioning adjacent vertebralbodies of two adjacent vertebrae adjacent a disc space in selectedrelationship to each other, said spinal distractor comprising: a bodyhaving a height adapted to be greater than the height of the disc space;and at least one disc penetrating extension extending from said bodyadapted to be inserted into the lateral aspect of the disc space from aposition anterior to the transverse processes of the adjacent vertebrae,said disc penetrating extension having a portion adapted to bear againsteach of the adjacent endplates of the two adjacent vertebral bodies,said portion of said disc penetrating extension having a height lessthan the height of said body and a length that is less than thetransverse width of the vertebral bodies between which said discpenetrating extension is adapted to be inserted, said length beinggreater than the depth of the spinal disc intermediate the two adjacentvertebral bodies between which said disc penetrating extension isadapted to be inserted.
 2. The spinal distractor of claim 1, furthercomprising means for limiting the penetration of said disc penetratingextension into the disc space.
 3. The spinal distractor of claim 2,wherein said limiting means comprises a shoulder on said body at thejuncture of said disc penetrating extension and said body for preventingsaid body from entering the disc space.
 4. The spinal distractor ofclaim 1, wherein said disc penetrating extension has a tapered front endto facilitate insertion of said disc penetrating extension into the discspace.
 5. The spinal distractor of claim 1, wherein said body has alongitudinal passageway adapted to receive an alignment pin.
 6. Thespinal distractor of claim 1, wherein said body has means for engagingan extraction device for extracting said disc penetrating extension fromthe disc space.
 7. The spinal distractor of claim 6, wherein saidengaging means includes a mating member for mating with an extractiondevice.
 8. An apparatus for use in spinal fusion surgery, said apparatuscomprising: a spinal distractor for positioning adjacent vertebralbodies of two adjacent vertebrae adjacent a disc space in selectedrelationship to each other, said spinal distractor comprising: a bodyhaving a height greater than the height of the disc space; and at leastone disc penetrating extension extending from said body for insertioninto the lateral aspect of the disc space from a position anterior tothe transverse processes of the adjacent vertebrae, said discpenetrating extension having a portion for bearing against each of theadjacent endplates of the two adjacent vertebral bodies, said portion ofsaid disc penetrating extension having a height less than the height ofsaid body and a length that is less than the transverse width of thevertebral bodies, said length being greater than the depth of the spinaldisc intermediate the two adjacent vertebral bodies between which saiddisc penetrating extension is inserted; and a guard having an openingfor providing protected access to the disc space and the adjacentvertebral bodies, said spinal distractor passing through said opening.9. The spinal distractor and guard combination of claim 8, wherein saidguard maintains said spinal distractor in coaxial alignment with thelongitudinal axis of the opening.
 10. The spinal distractor and guardcombination of claim 9, further in combination with a spinal implanthaving upper and lower surfaces for bearing upon and supporting each ofthe two adjacent vertebral bodies, said spinal implant passing throughsaid opening of said guard.
 11. The spinal distractor, guard, and spinalimplant combination of claim 10, wherein said guard maintains saidspinal implant in coaxial alignment with the longitudinal axis of theopening of said guard.
 12. The spinal distractor and guard combinationof claim 8, further in combination with a bone removal device having aportion sized for passage through said opening of said guard for formingthrough said guard an implantation space across the disc space.
 13. Thespinal distractor, guard, and bone removal device combination of claim12, further in combination with an implant driver having means forengaging an implant, said implant driver having a portion sized forpassage through said opening of said guard for passing an implantthrough said guard.
 14. An apparatus for use in human spinal surgeryacross the height of a disc space between the vertebral bodies of twoadjacent vertebrae, said apparatus comprising: a guard member having aheight adapted to be greater than the height of the disc space and anopening for providing protected access to the lateral aspect of the discspace and the adjacent vertebral bodies from a position anterior to thetransverse processes of the adjacent vertebrae, said opening having amaximum height; and at least one disc penetrating extension extendingfrom said guard member adapted to be inserted into the lateral aspect ofthe disc space from a position anterior to the transverse processes ofthe adjacent vertebrae, said disc penetrating extension having a portionadapted to bear against each of the adjacent endplates of the adjacentvertebral bodies, said portion of said disc penetrating extension havinga height less than the height of said guard member and a length that isless than the transverse width of the vertebral bodies between whichsaid disc penetrating extension is adapted to be inserted, said lengthbeing greater than the depth of the disc space in which said length isadapted to be inserted, said portion of said disc penetrating extensionhaving an upper surface adapted to contact one of the adjacent endplatesof the adjacent vertebral bodies and a lower surface adapted to contactthe other of the adjacent endplates of the adjacent vertebral bodies atmore than one point through the disc space.
 15. The apparatus of claim14, wherein said upper and lower surfaces are at least in part parallelto each other.
 16. The apparatus of claim 14, wherein said guard memberhas an external surface at its distal end and said disc penetratingextension is at least in part coextensive with said external surface.17. The apparatus of claim 14, further comprising a second discpenetrating extension extending from said guard member for insertioninto the disc space and for bearing against the endplates of theadjacent vertebral bodies.
 18. The apparatus of claim 17, wherein saiddisc penetrating extensions are diametrically opposed to each other. 19.The apparatus of claim 17, wherein said disc penetrating extensions havethe same height.
 20. An apparatus for use in human spinal surgery acrossa disc space between the vertebral bodies of two adjacent vertebrae,comprising: a guard member having a height greater than the height ofthe disc space and an opening for providing protected access to thelateral aspect of the disc space and the adjacent vertebral bodies froma position anterior to the transverse processes of the adjacentvertebrae, said opening having a maximum height; and at least two discpenetrating extensions extending from said guard member for insertioninto the lateral aspect of the disc space from a position anterior tothe transverse processes of the adjacent vertebrae, said discpenetrating extensions having a portion for bearing against each of theadjacent endplates of the adjacent vertebral bodies, said portion ofsaid disc penetrating extensions having a height less than the height ofsaid guard member and a length that is less than the transverse width ofthe vertebral bodies, said length being greater than the depth of thedisc space, said portion of said disc penetrating extensions having anupper surface adapted to contact one of the adjacent endplates of theadjacent vertebral bodies and a lower surface adapted to contact theother of the adjacent endplates of the adjacent vertebral bodies at morethan one point through the disc space, said disc penetrating extensionsbeing of a different height.
 21. An apparatus for use in human spinalsurgery across a disc space between the vertebral bodies of two adjacentvertebrae, comprising: a guard member having a height greater than theheight of the disc space and an opening for providing protected accessto the lateral aspect of the disc space and the adjacent vertebralbodies from a position anterior to the transverse processes of theadjacent vertebrae, said opening having a maximum height; and at leasttwo disc penetrating extensions extending from said guard member forinsertion into the lateral aspect of the disc space from a positionanterior to the transverse processes of the adjacent vertebrae, saiddisc penetrating extensions having a portion for bearing against each ofthe adjacent endplates of the adjacent vertebral bodies, said portion ofsaid disc penetrating extensions having a height less than the height ofsaid guard member and a length that is less than the transverse width ofthe vertebral bodies, said length being greater than the depth of thedisc space, said portion of said disc penetrating extensions having anupper surface adapted to contact one of the adjacent endplates of theadjacent vertebral bodies and a lower surface adapted to contact theother of the adjacent endplates of the adjacent vertebral bodies at morethan one point through the disc space, said disc penetrating extensionsbeing of a different length.
 22. The apparatus of claim 14, wherein saidportion of said disc penetrating extension has a height between saidupper and lower surfaces that approximates the height of the normal discspace between the adjacent vertebral bodies.
 23. The apparatus of claim14, wherein said guard member conforms at least in part to the exteriorsurface of the vertebral bodies of the lateral aspect of the adjacentvertebral bodies.
 24. The apparatus of claim 23, wherein said upper andlower surfaces are at least in part parallel to each other.
 25. Theapparatus of claim 23, further comprising a second disc penetratingextension extending from said guard member for insertion into the discspace and for bearing against the endplates of the adjacent vertebralbodies.
 26. The apparatus of claim 25, wherein said disc penetratingextensions are diametrically opposed to each other.
 27. The apparatus ofclaim 25, wherein said disc penetrating extensions have the same height.28. The apparatus of claim 25, wherein said disc penetrating extensionsare of a different height.
 29. The apparatus of claim 25, wherein saiddisc penetrating extensions are of a different length.
 30. The apparatusof claim 23, wherein said portion of said disc penetrating extension hasa height between said upper and lower surfaces that approximates theheight of the normal disc space between the adjacent vertebral bodies.31. The apparatus of claim 14, further comprising means for penetratingthe two adjacent vertebral bodies.
 32. The apparatus of claim 31,wherein said penetrating means includes teeth for insertion into thespine.
 33. The apparatus of claim 31, wherein said penetrating meansincludes at least one prong for insertion into the spine.
 34. Theapparatus of claim 14, further comprising a removable inner sleeve. 35.The apparatus of claim 14, further comprising means for limiting thedepth of penetration of said disc penetrating extension into the discspace.
 36. The apparatus of claim 14, wherein said guard membercomprises a hollow tube.
 37. An apparatus for use in human spinalsurgery across a disc space between the vertebral bodies of two adjacentvertebrae, comprising: a guard member including a hollow tube having aheight greater than the height of the disc space and an opening forproviding protected access to the lateral aspect of the disc space andthe adjacent vertebral bodies from a position anterior to the transverseprocesses of the adjacent vertebrae, said opening having a maximumheight, said hollow tube having a detachable distal end portion; and atleast one disc penetrating extension extending from said guard memberfor insertion into the lateral aspect of the disc space from a positionanterior to the transverse processes of the adjacent vertebrae, saiddisc penetrating extension having a portion for bearing against each ofthe adjacent endplates of the adjacent vertebral bodies, said portion ofsaid disc penetrating extension having a height less than the height ofsaid guard member and a length that is less than the transverse width ofthe vertebral bodies, said length being greater than the depth of thedisc space, said portion of said disc penetrating extension having anupper surface adapted to contact one of the adjacent endplates of theadjacent vertebral bodies and a lower surface adapted to contact theother of the adjacent endplates of the adjacent vertebral bodies at morethan one point through the disc space.
 38. The apparatus of claim 14,wherein said disc penetrating extension has a tapered leading end tofacilitate placement of said disc penetrating extension into the discspace.
 39. The apparatus of claim 14 in combination with a bone removaldevice having a portion sized for passage through said opening of saidguard for forming through said opening of said guard member animplantation space across the disc space.
 40. The apparatus of claim 39in combination with an implant driver sized in part for passage throughsaid opening of said guard for passing an implant through said guardmember and into the disc space.
 41. The apparatus of claim 14 incombination with a spinal distractor sized for passage through saidguard member, said spinal distractor having a body and a discpenetrating member extending from said body and into the disc spacebetween the two adjacent vertebral bodies for bearing against theadjacent endplates of the two adjacent vertebral bodies.
 42. Theapparatus of claim 41, wherein said disc penetrating member has atapered leading end to facilitate placement of said disc penetratingmember into the disc space.
 43. The apparatus of claim 14 in combinationwith a tap for insertion through said guard member for tapping the twoadjacent vertebral bodies.
 44. An apparatus for use in human spinalsurgery across a disc space between the vertebral bodies of two adjacentvertebrae, comprising: a guard member having a height greater than theheight of the disc space and an opening for providing protected accessto the lateral aspect of the disc space and the adjacent vertebralbodies from a position anterior to the transverse processes of theadjacent vertebrae, said opening having a maximum height; at least onedisc penetrating extension extending from said guard member forinsertion into the lateral aspect of the disc space from a positionanterior to the transverse processes of the adjacent vertebrae, saiddisc penetrating extension having a portion for bearing against each ofthe adjacent endplates of the adjacent vertebral bodies, said portion ofsaid disc penetrating extension having a height less than the height ofsaid guard member and a length that is less than the transverse width ofthe vertebral bodies, said length being greater than the depth of thedisc space, said portion of said disc penetrating extension having anupper surface adapted to contact one of the adjacent endplates of theadjacent vertebral bodies and a lower surface adapted to contact theother of the adjacent endplates of the adjacent vertebral bodies at morethan one point through the disc space; and an extractor coupler havingone end adapted to couple with said guard member and an opposite endadapted to couple with an extraction device.
 45. An apparatus for use inhuman interbody spinal surgery across a disc space between the vertebralbodies of two adjacent vertebrae, comprising: a guard member having aproximal end, a distal end, a height greater than the height of the discspace, and at least one passageway adapted to permit the passage of abone removal device therethrough for providing protected access to thedisc space and the adjacent vertebral bodies, said passage having amaximum height; and at least one disc penetrating extension extendingfrom said distal end of said guard member for insertion into the discspace, said disc penetrating extension being separable from saidproximal end of said guard, said disc penetrating extension having aportion for bearing against each of the adjacent endplates of theadjacent vertebral bodies, said portion of said disc penetratingextension having an upper surface adapted to contact one of the adjacentendplates of the adjacent vertebral bodies and a lower surface adaptedto contact the other of the adjacent endplates of the adjacent vertebralbodies intermediate the two adjacent vertebral bodies between which saiddisc penetrating extension is inserted.
 46. The apparatus of claim 20,wherein said upper and lower surfaces are at least in part parallel toeach other.
 47. The apparatus of claim 20, wherein said guard member hasan external surface at its distal end and said disc penetratingextensions are at least in part coextensive with said external surface.48. The apparatus of claim 20, wherein said disc penetrating extensionsare diametrically opposed to each other.
 49. The apparatus of claim 20,wherein said disc penetrating extensions are of a different length. 50.The apparatus of claim 20, wherein said portion of said disc penetratingextension has a height between said upper and lower surfaces thatapproximates the height of the normal disc space between the adjacentvertebral bodies.
 51. The apparatus of claim 20, wherein said guardmember conforms at least in part to the exterior surface of thevertebral bodies of the lateral aspect of the adjacent vertebral bodies.52. The apparatus of claim 20, further comprising means for penetratingthe two adjacent vertebral bodies.
 53. The apparatus of claim 52,wherein said penetrating means includes teeth for insertion into thespine.
 54. The apparatus of claim 52, wherein said penetrating meansincludes at least one prong for insertion into the spine.
 55. Theapparatus of claim 20, further comprising a removable inner sleeve. 56.The apparatus of claim 20, further comprising means for limiting thedepth of penetration of said disc penetrating extensions into the discspace.
 57. The apparatus of claim 20, wherein said guard membercomprises a hollow tube.
 58. The apparatus of claim 57, wherein saidhollow tube has a detachable distal end portion.
 59. The apparatus ofclaim 20, wherein said disc penetrating extensions have a taperedleading end to facilitate placement of said disc penetrating extensionsinto the disc space.
 60. The apparatus of claim 20 in combination with abone removal device having a portion sized for passage through saidopening of said guard for forming through said opening of said guardmember an implantation space across the disc space.
 61. The apparatus ofclaim 20 in combination with an implant driver sized in part for passagethrough said opening of said guard for passing an implant through saidguard member and into the disc space.
 62. The apparatus of claim 20 incombination with a spinal distractor sized for passage through saidguard member, said spinal distractor having a body and a discpenetrating member extending from said body and into the disc spacebetween the two adjacent vertebral bodies for bearing against theadjacent endplates of the two adjacent vertebral bodies.
 63. Theapparatus of claim 62, wherein said disc penetrating member has atapered leading end to facilitate placement of said disc penetratingmember into the disc space.
 64. The apparatus of claim 20 in combinationwith a tap for insertion through said guard member for tapping the twoadjacent vertebral bodies.
 65. The apparatus of claim 20, furthercomprising an extractor coupler having one end adapted to couple withsaid guard member and an opposite end adapted to couple with anextraction device.
 66. The apparatus of claim 21, wherein said upper andlower surfaces are at least in part parallel to each other.
 67. Theapparatus of claim 21, wherein said guard member has an external surfaceat its distal end and said disc penetrating extensions are at least inpart coextensive with said external surface.
 68. The apparatus of claim20, wherein said disc penetrating extensions have the same height. 69.The apparatus of claim 21, wherein said disc penetrating extensions arediametrically opposed to each other.
 70. The apparatus of claim 21,wherein said portion of said disc penetrating extension has a heightbetween said upper and lower surfaces that approximates the height ofthe normal disc space between the adjacent vertebral bodies.
 71. Theapparatus of claim 21, wherein said guard member conforms at least inpart to the exterior surface of the vertebral bodies of the lateralaspect of the adjacent vertebral bodies.
 72. The apparatus of claim 21,further comprising means for penetrating the two adjacent vertebralbodies.
 73. The apparatus of claim 72, wherein said penetrating meansincludes teeth for insertion into the spine.
 74. The apparatus of claim72, wherein said penetrating means includes at least one prong forinsertion into the spine.
 75. The apparatus of claim 21, furthercomprising a removable inner sleeve.
 76. The apparatus of claim 21,further comprising means for limiting the depth of penetration of saiddisc penetrating extensions into the disc space.
 77. The apparatus ofclaim 21, wherein said guard member comprises a hollow tube.
 78. Theapparatus of claim 77, wherein said hollow tube has a detachable distalend portion.
 79. The apparatus of claim 21, wherein said discpenetrating extensions have a tapered leading end to facilitateplacement of said disc penetrating extensions into the disc space. 80.The apparatus of claim 21 in combination with a bone removal devicehaving a portion sized for passage through said opening of said guardfor forming through said opening of said guard member an implantationspace across the disc space.
 81. The apparatus of claim 21 incombination with an implant driver sized in part for passage throughsaid opening of said guard for passing an implant through said guardmember and into the disc space.
 82. The apparatus of claim 21 incombination with a spinal distractor sized for passage through saidguard member, said spinal distractor having a body and a discpenetrating member extending from said body and into the disc spacebetween the two adjacent vertebral bodies for bearing against theadjacent endplates of the two adjacent vertebral bodies.
 83. Theapparatus of claim 82, wherein said disc penetrating member has atapered leading end to facilitate placement of said disc penetratingmember into the disc space.
 84. The apparatus of claim 21 in combinationwith a tap for insertion through said guard member for tapping the twoadjacent vertebral bodies.
 85. The apparatus of claim 21, furthercomprising an extractor coupler having one end adapted to couple withsaid guard member and an opposite end adapted to couple with anextraction device.
 86. The apparatus of claim 37, wherein said upper andlower surfaces are at least in part parallel to each other.
 87. Theapparatus of claim 37, wherein said guard member has an external surfaceat its distal end and said disc penetrating extension is at least inpart coextensive with said external surface.
 88. The apparatus of claim37, further comprising a second disc penetrating extension extendingfrom said guard member for insertion into the disc space and for bearingagainst the endplates of the adjacent vertebral bodies.
 89. Theapparatus of claim 88, wherein said disc penetrating extensions arediametrically opposed to each other.
 90. The apparatus of claim 88,wherein said disc penetrating extensions have the same height.
 91. Theapparatus of claim 88, wherein said disc penetrating extensions are of adifferent height.
 92. The apparatus of claim 88, wherein said discpenetrating extensions are of a different length.
 93. The apparatus ofclaim 37, wherein said portion of said disc penetrating extension has aheight between said upper and lower surfaces that approximates theheight of the normal disc space between the adjacent vertebral bodies.94. The apparatus of claim 37, wherein said guard member conforms atleast in part to the exterior surface of the vertebral bodies of thelateral aspect of the adjacent vertebral bodies.
 95. The apparatus ofclaim 94, wherein said upper and lower surfaces are at least in partparallel to each other.
 96. The apparatus of claim 94, furthercomprising a second disc penetrating extension extending from said guardmember for insertion into the disc space and for bearing against theendplates of the adjacent vertebral bodies.
 97. The apparatus of claim96, wherein said disc penetrating extensions are diametrically opposedto each other.
 98. The apparatus of claim 96, wherein said discpenetrating extensions have the same height.
 99. The apparatus of claim96, wherein said disc penetrating extensions are of a different height.100. The apparatus of claim 96, wherein said disc penetrating extensionsare of a different length.
 101. The apparatus of claim 94, wherein saidportion of said disc penetrating extension has a height between saidupper and lower surfaces that approximates the height of the normal discspace between the adjacent vertebral bodies.
 102. The apparatus of claim37, further comprising means for penetrating the two adjacent vertebralbodies.
 103. The apparatus of claim 102, wherein said penetrating meansincludes teeth for insertion into the spine.
 104. The apparatus of claim102, wherein said penetrating means includes at least one prong forinsertion into the spine.
 105. The apparatus of claim 37, furthercomprising a removable inner sleeve.
 106. The apparatus of claim 37,further comprising means for limiting the depth of penetration of saiddisc penetrating extension into the disc space.
 107. The apparatus ofclaim 37, wherein said disc penetrating extension has a tapered leadingend to facilitate placement of said disc penetrating extension into thedisc space.
 108. The apparatus of claim 37 in combination with a boneremoval device having a portion sized for passage through said openingof said guard for forming through said opening of said guard member animplantation space across the disc space.
 109. The apparatus of claim 37in combination with an implant driver sized in part for passage throughsaid opening of said guard for passing an implant through said guardmember and into the disc space.
 110. The apparatus of claim 37 incombination with a spinal distractor sized for passage through saidguard member, said spinal distractor having a body and a discpenetrating member extending from said body and into the disc spacebetween the two adjacent vertebral bodies for bearing against theadjacent endplates of the two adjacent vertebral bodies.
 111. Theapparatus of claim 110, wherein said disc penetrating member has atapered leading end to facilitate placement of said disc penetratingmember into the disc space.
 112. The apparatus of claim 37 incombination with a tap for insertion through said guard member fortapping the two adjacent vertebral bodies.
 113. The apparatus of claim37, further comprising an extractor coupler having one end adapted tocouple with said guard member and an opposite end adapted to couple withan extraction device.
 114. The apparatus of claim 45, wherein said upperand lower surfaces are at least in part parallel to each other.
 115. Theapparatus of claim 45, wherein said guard member has an external surfaceat its distal end and said disc penetrating extension is at least inpart coextensive with said external surface.
 116. The apparatus of claim45, further comprising a second disc penetrating extension extendingfrom said guard member for insertion into the disc space and for bearingagainst the endplates of the adjacent vertebral bodies.
 117. Theapparatus of claim 116, wherein said disc penetrating extensions arediametrically opposed to each other.
 118. The apparatus of claim 116,wherein said disc penetrating extensions have the same height.
 119. Theapparatus of claim 116, wherein said disc penetrating extensions are ofa different height.
 120. The apparatus of claim 116, wherein said discpenetrating extensions are of a different length.
 121. The apparatus ofclaim 45, wherein said portion of said disc penetrating extension has aheight between said upper and lower surfaces that approximates theheight of the normal disc space between the adjacent vertebral bodies.122. The apparatus of claim 45, wherein said guard member conforms atleast in part to the exterior surface of the vertebral bodies of thelateral aspect of the adjacent vertebral bodies.
 123. The apparatus ofclaim 122, wherein said upper and lower surfaces are at least in partparallel to each other.
 124. The apparatus of claim 122, furthercomprising a second disc penetrating extension extending from said guardmember for insertion into the disc space and for bearing against theendplates of the adjacent vertebral bodies.
 125. The apparatus of claim124, wherein said disc penetrating extensions are diametrically opposedto each other.
 126. The apparatus of claim 124, wherein said discpenetrating extensions have the same height.
 127. The apparatus of claim124, wherein said disc penetrating extensions are of a different height.128. The apparatus of claim 124, wherein said disc penetratingextensions are of a different length.
 129. The apparatus of claim 122,wherein said portion of said disc penetrating extension has a heightbetween said upper and lower surfaces that approximates the height ofthe normal disc space between the adjacent vertebral bodies.
 130. Theapparatus of claim 45, further comprising means for penetrating the twoadjacent vertebral bodies.
 131. The apparatus of claim 130, wherein saidpenetrating means includes teeth for insertion into the spine.
 132. Theapparatus of claim 130, wherein said penetrating means includes at leastone prong for insertion into the spine.
 133. The apparatus of claim 45,further comprising means for limiting the depth of penetration of saiddisc penetrating extension into the disc space.
 134. The apparatus ofclaim 45, wherein said disc penetrating extension has a tapered leadingend to facilitate placement of said disc penetrating extension into thedisc space.
 135. The apparatus of claim 45 in combination with a boneremoval device having a portion sized for passage through saidpassageway of said guard for forming through said passageway of saidguard member an implantation space across the disc space.
 136. Theapparatus of claim 45 in combination with an implant driver sized inpart for passage through said passageway of said guard for passing animplant through said guard member and into the disc space.
 137. Theapparatus of claim 45 in combination with a spinal distractor sized forpassage through said guard member, said spinal distractor having a bodyand a disc penetrating member extending from said body and into the discspace between the two adjacent vertebral bodies for bearing against theadjacent endplates of the two adjacent vertebral bodies.
 138. Theapparatus of claim 137, wherein said disc penetrating member has atapered leading end to facilitate placement of said disc penetratingmember into the disc space.
 139. The apparatus of claim 45 incombination with a tap for insertion through said guard member fortapping the two adjacent vertebral bodies.
 140. The apparatus of claim45, further comprising an extractor coupler having one end adapted tocouple with said guard member and an opposite end adapted to couple withan extraction device.
 141. The apparatus of claim 45, wherein saidportion of said disc penetrating extension has a height less than theheight of said passage.
 142. A spinal instrument assembly, comprising: acentral distractor having a distractor tip coupled to a shaft, saiddistractor tip having upper and lower distraction surfaces defining adistraction height therebetween to maintain distraction of a spinal discspace; a guide sleeve housing having a distal portion and a proximalportion, said guide sleeve housing defining a working channel in whichsaid central distractor is centrally located, wherein said guide sleevehousing is positionable in an operative position with respect to thespinal disc space; and a guide sleeve having a distal end and a proximalend, said distal end of said guide sleeve removably engageable to saidguide sleeve housing.
 143. The instrument assembly of claim 142, whereinsaid central distractor is withdrawable from the spinal disc space andsaid guide sleeve housing when said guide sleeve housing is in saidoperative position.
 144. The instrument assembly of claim 142, wherein:said guide sleeve has a first length extending proximally from saidguide sleeve housing when engaged thereto; said guide sleeve housing hasa second length extending proximally from the operative site; and aratio of said first length to said second length is more than about 2:1.145. The instrument assembly of 144, wherein said ratio is less thanabout 10:1.
 146. The apparatus of claim 141, wherein said at least onedisc penetrating extension has a length that is less than the transversewidth of the vertebral bodies, said length being greater than the depthof the spinal disc intermediate the two adjacent vertebral bodiesbetween which said disc penetrating extension is inserted.